Several years ago, I caught one of my kids sneaking out of the house. Like any mom, I was more than a little mad and demanded an explanation. "But Mom, I wasn't doing anything wrong -- I was just hanging out with my friends," was the response I got, but I knew better. The truth is that if you don't have anything to be ashamed of, you have no reason to be sneaking around.

This election season, special interests are sneaking around trying to influence voters by funding the attack ads you see on TV. With the help of a recent court ruling, they can do it all anonymously. It's hard not to think it's because they have something to be ashamed of.

In January, the Supreme Court gave corporations, unions and special interest groups the power to influence elections in an unlimited and anonymous way. In an unprecedented move, the court, the same majority who decried an activist court when they were nominees, legislated from the bench and overturned years of previous case law, striking down longstanding limitations on campaign spending from special interests in the case of Citizens United v. Federal Election Commission.

Before Citizens United, corporations and unions could not spend money to run ads expressly advocating one candidate over another. Now they can. But what is worse, they can anonymously donate millions of dollars to "nonprofit" groups, which buy the ads without having to disclose who truly paid for them. The ruling essentially opened the barn door to anonymous, unlimited corporate donations to sway voters.

Americans have a lot to be frustrated about right now with our economy, and I know many are anxiously awaiting their opportunity to weigh in on the country's future by voting on November 2. The idea that special interests are trying to secretly buy this election should make their blood boil.

The idea that special interests are trying to secretly buy this election should make [voters'] blood boil.
--Sen. Claire McCaskill

Although every member of Congress should be trying to stop this, that is not the case. Republicans have blocked legislation that would help bring these donors to light. A bill offered by Sen. Chuck Schumer, which I co-sponsored, would have forced corporations and unions that want to spend money on campaign ads to be transparent with the public about their political contributions and their donors, while also banning political spending from foreign entities. But each time the bill has received a vote, Republicans have made sure it failed.

This bill wouldn't favor one side or the other: From the most conservative groups to the most liberal, any special interest group spending money on campaign ads would have to be honest about where their funding comes from so voters know whose interest they really represent.

Republicans spend a lot of time decrying activist court decisions, yet when it comes to overturning campaign limits and disclosure rules for special interests, they seem to have changed their minds. The reality is that special interests are trying to buy our government this cycle, and Republicans think that's OK. Well, I don't.

My position is simple: If you are for someone or something, you should be willing to say it out loud. The voters deserve to know. Right now, these shadowy organizations are refusing to produce a list of their donors, and that's something voters need to consider in November. My rule of thumb is, if I can't find out who's paying for the ad, I don't believe it.

When my teenager tried to pull a fast one on me, I said if you're not willing to own up to it, how do I know you're not doing something wrong? This election cycle, special interests are trying to get away with buying this election without being held accountable. Until they are more forthcoming with where the money is coming from, how can voters believe a word they say?

The opinions expressed in this commentary are solely those of Sen. Claire McCaskill.